Linear (Synonymous with In-Line, just faster to say, and type) Staging is how we've always done it, except the experiment in Parallel Staging with the Space Shuttles. It has it's own intrinsic advantages, and disadvantages like any other technique.

This kind of staging at least doubles the weight of the craft, by replicating everything, engines, wings, fuel tanks, even cockpit, and life support if both stages (Assuming only 2 stages) are Crewed. An Air-breathing first stage mitigates this somewhat by eliminating the Oxydizer tank, but that's a small relative mass fraction (Approximately 1 3/4 instead of double with current technology/designs.)

Parallel Staging (Both sections thrust at once, like the SMEs, and SRBs, though one could be converted to Air breathing theoretically) has higher drag, and larger footprint, but doesn't require as tall a stack, and therefore assembly, and support structures for launch.

The ideal (Which is beyond current technology, and designs) is an OStEO, or SSTO (I use One Stage to Earth Orbit, almost exclusively) that does it all in one shot, but the challenge is to make an engine that's capable, and efficient throughout the surface-to-orbit flight. If we're talking vertical launch, first it has to get going from a dead stop, straight up which is honestly the greatest hemorrage of fuel.

This can't be done with an Air breathing Engine unless it intakes at a standstill (Which means Turbojets instead of Ramjets, or Pulsejets.) A Ram/Rocket approach could launch on rocket power (With a disposable Tank, making it technically a Stage and a half) until gaining enough airspeed for the ram effect. In the Atmosphere, this is ideal, because you can shrink the Oxydizer Tank, and make up for Drag by gaining energy from it. Once you leave the atmosphere (or gain enough altitude for it to be miniscule) you have to operate as a Rocket because there's nothing else to push against than you own exhaust.

So, the primary challenge to not Staging is to make an engine that can operate with ram-air, and as an oxydized rocket, not to mention thrusting efficiently at all altitudes. The next hurdle is a nozzle that runs efficiently at all ambient air pressures from sea level to relative vaccuum. I believe a fuel swith will also be needed, because the best reaction mass at low altitude is dense (Ideally something like Mercury Vapor if it wouldn't be so pollutant) while in a Vaccuum you want something as light as possible traveling damned near the Speed of light (Hydrogen, protons, electrons, neutrinos...)

I kind of got off on a tangent with OStEOs, because staging is pretty much a compromise like Hybrid Cars. What we really need are full Electrics, but our energy storage isn't there yet, so we try to mitigate the gas milage by efficiency. We'll probably see Fuel Cells before full battery models capable of directly competing in mass, capacity, range, and speed. Likewise, it would be nice if we had a flex fuel aerospike ram/rocket, but we don't, so we're still stuck building an engine cluster for each stage of the flight, and throwing them away as we ascend.

This proposal seems to be making the lift/take off booster capable of flying back, and being refueled like the winged orbiter (Spaceplane.) I guess that's a step in the right direction, but it's not where we're ultimately headded...

_________________"You can't have everything, where would you put it?" -Steven Wright.

Reaction Engines has got you covered there, all the way from 0 to Mach 5 on outside air and LH2, then LH2/LOX for the final push into orbit. They've got a design for an SSTO craft to go with it to, and some scaled down working demonstration hardware for the key pieces of the engine. The question is if they will be able to find the funding to develop the full space plane though.

In-line staging has potential aerodynamic advantages I would guess, but structurally it's more tricky I think. The Hermes space plane was supposed to launch on Ariane 5, but the booster was single-use and launched vertically; similar to the current Dream Chaser/EELV stack. I seem to recall a HOTOL/Sänger combination that would have the HOTOL space plane (incidentally designed by Alan Bond, the key engineer behind the above mentioned Reaction Engines) take off from the back of the Sänger hypersonic plane, but can't find anything on it right now. Here's a page that includes both of them at least, listing HOTOL as an SSTO. But if they can make it fly without falling apart, well it does look very cool .

Edit: fixed link.

_________________Say, can you feel the thunder in the air? Just like the moment ’fore it hits – then it’s everywhereWhat is this spell we’re under, do you care? The might to rise above it is now within your sphereMachinae Supremacy – Sid Icarus

Last edited by Lourens on Thu Apr 11, 2013 2:01 pm, edited 1 time in total.

Reaction Engines has got you covered there, all the way from 0 to Mach 5 on outside air and LH2, then LH2/LOX for the final push into orbit. They've got a design for an SSTO craft to go with it to, and some scaled down working demonstration hardware for the key pieces of the engine. The question is if they will be able to find the funding to develop the full space plane though.

In-line staging has potential aerodynamic advantages I would guess, but structurally it's more tricky I think. The Hermes space plane was supposed to launch on Ariane 5, but the booster was single-use and launched vertically; similar to the current Dream Chaser/EELV stack. I seem to recall a HOTOL/Sänger combination that would have the HOTOL space plane (incidentally designed by Alan Bond, the key engineer behind the above mentioned Reaction Engines) take off from the back of the Sänger hypersonic plane, but can't find anything on it right now. [url="http://www.vectorsite.net/tashutl_c08.html"]Here[/url]'s a page that includes both of them at least, listing HOTOL as an SSTO. But if they can make it fly without falling apart, well it does look very cool .

You know the Sänger was a design for the Nazis to bomb Amerika, right? Not really a Godwin thing, they knew how to build stuff in Germany around that time, where we got Goddard, Oppenheimer, and Braun from, but I just kind of have to think that our next cutting edge aero/space workhorse should probably be a more recent design than over Half a Century.

_________________"You can't have everything, where would you put it?" -Steven Wright.

Linear (Synonymous with In-Line, just faster to say, and type) Staging is how we've always done it, except the experiment in Parallel Staging with the Space Shuttles. It has it's own intrinsic advantages, and disadvantages like any other technique.

This kind of staging at least doubles the weight of the craft, by replicating everything, engines, wings, fuel tanks, even cockpit, and life support if both stages (Assuming only 2 stages) are Crewed. An Air-breathing first stage mitigates this somewhat by eliminating the Oxydizer tank, but that's a small relative mass fraction (Approximately 1 3/4 instead of double with current technology/designs.)

Parallel Staging (Both sections thrust at once, like the SMEs, and SRBs, though one could be converted to Air breathing theoretically) has higher drag, and larger footprint, but doesn't require as tall a stack, and therefore assembly, and support structures for launch.

The ideal (Which is beyond current technology, and designs) is an OStEO, or SSTO (I use One Stage to Earth Orbit, almost exclusively) that does it all in one shot, but the challenge is to make an engine that's capable, and efficient throughout the surface-to-orbit flight. If we're talking vertical launch, first it has to get going from a dead stop, straight up which is honestly the greatest hemorrage of fuel.

This can't be done with an Air breathing Engine unless it intakes at a standstill (Which means Turbojets instead of Ramjets, or Pulsejets.) A Ram/Rocket approach could launch on rocket power (With a disposable Tank, making it technically a Stage and a half) until gaining enough airspeed for the ram effect. In the Atmosphere, this is ideal, because you can shrink the Oxydizer Tank, and make up for Drag by gaining energy from it. Once you leave the atmosphere (or gain enough altitude for it to be miniscule) you have to operate as a Rocket because there's nothing else to push against than you own exhaust.

So, the primary challenge to not Staging is to make an engine that can operate with ram-air, and as an oxydized rocket, not to mention thrusting efficiently at all altitudes. The next hurdle is a nozzle that runs efficiently at all ambient air pressures from sea level to relative vaccuum. I believe a fuel swith will also be needed, because the best reaction mass at low altitude is dense (Ideally something like Mercury Vapor if it wouldn't be so pollutant) while in a Vaccuum you want something as light as possible traveling damned near the Speed of light (Hydrogen, protons, electrons, neutrinos...)

I kind of got off on a tangent with OStEOs, because staging is pretty much a compromise like Hybrid Cars. What we really need are full Electrics, but our energy storage isn't there yet, so we try to mitigate the gas milage by efficiency. We'll probably see Fuel Cells before full battery models capable of directly competing in mass, capacity, range, and speed. Likewise, it would be nice if we had a flex fuel aerospike ram/rocket, but we don't, so we're still stuck building an engine cluster for each stage of the flight, and throwing them away as we ascend.

This proposal seems to be making the lift/take off booster capable of flying back, and being refueled like the winged orbiter (Spaceplane.) I guess that's a step in the right direction, but it's not where we're ultimately headded...

I can't wait for skylon to be operational, if it ever will be.

I think though that it wouldn't hurt to work on other approaches to cheap access to space. If this could be developed using nearly off the shelf technologies, it might be worth a try.

It offers the advantage of properly reusing the hardware, the advantage of possible quick turnaround of at least the first stage, and improved safety in case of engine failiure.

This design might fit in quite well with the Skylon, and VTOL rockets. I mean they all could potentially reduce launch costs while also offering technological know how that could be further built upon.

For instance using sabre engines but instead of an SSTO do linear staging.

Wouldn't that increase the payload that can be carried to orbit?

Or what about the advantage of not having a bulky large body to do intricate manouvers with around space stations. Also the main stage can go back straight away and wouldn't have to spend days or weeks in orbit while the mission is being carried out. So this could increase the amount of mass that could be launched in a short amount of time with the same vehicle.

Actually this last advantage might be the deal breaker between an ssto and a staged winged system. The first stage returns within hours to be refueled, attached to another second stage, and then launched again. Meanwhile the second stage from the first launch is doing it's thing in orbit. When it returns, it gets checked out, refueled, reloaded with cargo, and can go on a ride again. So within the mission time of one ssto mission, one could launch several 2 staged missions because the main stage is constantly working instead of floating around doing nothing for days or weeks.

And last but not least horizontal launch would probably decrease the handling costs of the vehicles. You can just taxi around with them, no need for cranes and lifting the whole structure to a vertical position. The whole operation could be done nearly the same way we operate our airlines.

Questions: What would be the ascent profile be like for a horizontal take off and landing 2 staged rocket plane?

Could this carry cargo to orbit? Or rocket engines aren't really good enough for horizontal take off and landing?

Do we really need a SABRE engine /using H2 LOX/ for the main stage, or can we do away with just "normal" /lets say RP-1/LOX/ rocket engines on both stages?

And last but not least horizontal launch would probably decrease the handling costs of the vehicles. You can just taxi around with them, no need for cranes and lifting the whole structure to a vertical position. The whole operation could be done nearly the same way we operate our airlines.

Except those things add development and fabrication costs, plus you have a performance penalty from having to carry all those things with you during flight.

Quote:

Questions: What would be the ascent profile be like for a horizontal take off and landing 2 staged rocket plane?

Sorry, I was talking about Sänger II, not its WWII namesake. And I probably mixed up HOTOL with the Sänger II second stage, which was to be named Horus.

RP-1 is much heavier than H2, so less efficient, although you gain back a little bit because it will also let you accelerate faster thus reducing the duration of the trip to orbit, and with it gravity losses. LOX is also heavy, but we don't have any lighter oxidiser. SABRE solves that by getting the oxidiser from the surrounding atmosphere, so you don't have to lift it. But the maths works out so that even with H2/LOX an SSTO needs to have very light structures to have a usable payload mass. It's been pointed out in another thread that the Falcon 9 first stage, which uses RP-1/LOX, could make it into orbit on its own, but it couldn't bring anything along, so it's kind of pointless.

_________________Say, can you feel the thunder in the air? Just like the moment ’fore it hits – then it’s everywhereWhat is this spell we’re under, do you care? The might to rise above it is now within your sphereMachinae Supremacy – Sid Icarus

Unless of course your goal is just to get the mass of the launcher into orbit where you could use the tanks as pressurized compartments and the engines etc. as either in-space propulsion or simply to recycle the material into other things.

So if you can lift a rocket above most of the atmosphere, it won't need staging?

What I mean is, what percentage of the total deltaV is usually achieved by the first stage. Is the first stage mostly there to lift the second stage above most of the atmosphere and it's contribution to the horizontal velocity is minimal?

Quote:

The usual scheme is for the first stage/carrier to use air breathing engines to take advantage of the oxygen in the lower atmosphere.

The appeal of SABRE is that it promises to be able to use a single propulsion system and vehicle all the way up.

Staging, of any type, adds complexity, cost, and risk. It is done only because we have to for performance requirements.

I have been asking the silly questions cause I was wondering if a project like this could be done Copenhagen Suborbitals style. /if it was worth it to begin with/

With SpaceGAMBIT around, this could be a feasible project to go for. Though I think the projects cannot be about stuff regulated by export control if I remember correctly and a rocketplane and it's parts would still be covered by these regulations.

Damn it.

Anybody has any ideas regarding a possible orbital access method, that could be cheap, as well as not fall under current export control legistlations of various countries so it could be developed open source in a distributed manner among hackerspaces under SpaceGAMBIT or other future projects like it.

So if you can lift a rocket above most of the atmosphere, it won't need staging?

What I mean is, what percentage of the total deltaV is usually achieved by the first stage. Is the first stage mostly there to lift the second stage above most of the atmosphere and it's contribution to the horizontal velocity is minimal?

Both usually. With traditional rockets by the time you are above most of the atmosphere you are going at a pretty good clip, which is necessary to achieve orbit. The climb up contributes to horizontal velocity.

Quote:

Anybody has any ideas regarding a possible orbital access method, that could be cheap, as well as not fall under current export control legistlations of various countries so it could be developed open source in a distributed manner among hackerspaces under SpaceGAMBIT or other future projects like it.

ITAR et al. is designed and implemented with traditional commercial activity in mind. Ie; Company A wants to sell (export) something it developed that is on the munitions list to Company B or Country B that is in Country B. It really isn't structured to deal with "open" or collaboratively developed "amateur" projects that use publicly released technology and common knowledge, especially if you aren't trying to ship a rocket somewhere.

It is skirting the letter of the law, and no US company will play along, but it IS possible for YOU to build and fly something just with the information you get from the Internet.

There are attempts being made to lighten up some of the ITAR restrictions, while at the same time it is being expanded to include computer security...

Hey, Psiberzerker, I noticed that for your location you have: "Outside Wonko the Sane's house." Since I'm new to the forum I have to ask... would that really be "inside" since he lives "outside" the asylum? Or is it "outside" because you live "inside" the... never mind, I can no longer follow my own train of thought.

I like the idea of incorporating railgun technology into the design for a number of reasons... not least of all because there are numerous applications for the same technology well beyond the limits of our atmosphere (returning materials from the moon and asteroids for example).

There may be even more advantages if the launch rail was built high above sea level (e.g. higher velocity with less skin heating).

You do not have the required permissions to view the files attached to this post._________________The most promising new channel on YouTube: FargoFX(in my totally dispassionate and thoroughly objective opinion.)

Heh. Vertical launch is "dwindling into obsolescence"? That must be why SpaceX is rapidly developing new vertically launched rockets, NASA is building another big one, and Russia is currently setting up an entirely new launch site for them, while air launch is limited to suborbital and light orbital rockets, and uses subsonic aircraft for the first stage...

It's true that we can't really make chemical rockets much more efficient than the best ones we have right now. If nuclear is out, then air-breathing is a logical next step. We've managed to fly a few scramjets in the past couple of years, but they don't seem very reliable yet, and the problem is that you need a lot of speed to get them to light at all. Those experimental ones have a big rocket as a first stage to get them up to Mach 6 or so.

So you need something for that first boost. Conventional turbojets only go up to Mach 3 or so, above which you need a ramjet, but ramjets only work from Mach 1 onwards, so now you need three different engines to be able to do it from a runway. Or, as seems to be the plan in that article, a rail launch to Mach 1, then a ramjet up to Mach 6, then a scramjet up to Mach 10, and then a rocket-powered second (third?) stage. Even if you manage to combine the ramjet and scramjet into a single engine, it's still going to be a lot more complex and heavy than a rocket engine.

In the end, the key issue here (and that's what the Air Force is talking about in the article linked from the linked article ) is rapid reusability. Apparently, SpaceX is going to try to do a soft touchdown on water of the first stage on the upcoming F9 flights, and possibly a land landing in 2014. If they manage to do that, the Air Force's 2030s timeline will look silly indeed, and they'll end up standing in line in Hawthorne with everyone else instead.

The SpaceX reusable F9/FH will also be cheaper to build than an air breathing craft (an F9 launch, including rocket, currently costs $50M, which is less than 1/5 the cost of a Boeing 777, which has the same gross take-off weight), with only one (cheap, simple, light) type of engine, nearly identical first and second stages, and no wings or landing gear. So, it doesn't have to last that many flights, since you can just (profitably!) launch it in single-use mode with a bigger payload after a bunch of reuses, and then write it off. Or overhaul the engines, which is also cheaper for a simple rocket engine compared to a complex combined (sc)ramjet/turbojet engine.

So I say, long live vertical launch .

_________________Say, can you feel the thunder in the air? Just like the moment ’fore it hits – then it’s everywhereWhat is this spell we’re under, do you care? The might to rise above it is now within your sphereMachinae Supremacy – Sid Icarus

Elon hired a bunch of "old NASA hands" for the top positions at SpaceX. In addition to bringing connections with government and the aerospace industry that smoothed contracting, they also brought a conservative, pragmatic approach. That means that its technical solutions are also largely just incremental improvements over what everyone else has done/is doing.

Does not mean that it's the best or final solution. Only that it was a good solution for the time.